I have been mining the Zig Z1 for a couple of weeks now -- have tried a number of sites -- individual coins and multi-coin sites -- best I have come across so far a Prohash and Zpool.  I found suprnova had issues with the hashrate falling off precipitously, experienced a less severe gradual decline at blockmaster as well.  Zpool seems to be consistent however have to reboot machine every two to three days or so to keep hashrate up.  Running at 850mhs -- average hashrate 6-6.2.